Document that they can be modified using COPY as well.
Back-patch to v11 where commit
3d956d956 added support for COPY in
postgres_fdw.
Now you need only SELECT from a foreign table to access
the data stored in its underlying remote table. You can also modify
the remote table using INSERT, UPDATE,
- DELETE, or TRUNCATE.
+ DELETE, COPY, or
+ TRUNCATE.
(Of course, the remote user you have specified in your user mapping must
have privileges to do these things.)